especially irreplaceable role in the area of precision actuations, such as in lens driving in optical assemblies and optical communication, micro/nanopositioning in semiconductor and microelectromechanical system (MEMS) manufacturing, nanoscanning probes in scanning electron microscopy, etc. [1,2] Due to the huge market demand for piezoelectric actuators, the progress of piezoelectric materials and devices is new every year. New piezoelectric material compositions, novel fabrication processes and full assessments of materials are widely studied to improve the material properties or make devices more suitable for actuation applications. Pb(Zr,Ti)O 3 (PZT)-based ceramics are still dominant in the market because of their high piezoelectric properties, low cost, and stable thermal performance. Although single crystals' piezoelectric and electromechanical coupling coefficients show great advances compared with ceramics, actuation applications are limited to only some special cases due to high cost of single crystals. [3] Lead-free ceramics have also experienced fast development, and some compositions have been found to exhibit large strains, but they also result in large energy losses under high electric fields. This type of ceramic may have potential for use in nonresonant actuator applications. Additionally, various actuation configurations operating via different working modes or mechanisms have been developed.In this review, we first introduce materials used for the corresponding actuators and motors, and then, recent developments in the area of actuators including nonresonant multilayer ceramic actuators, step motors and inertial motors, and resonant ultrasonic motors, such as linear motors, rotary motors, multi-DOF motors, and MEMS actuators, are discussed. Actuation performance parameters such as the stroke length, resolution, loading force, velocity, lifetime, and power efficiency are the main concerns. We try to clarify and compare differences between devices. Finally, the challenges and outlook for the piezoelectric actuators are discussed.
Piezoelectric Materials for ActuatorsPiezoelectricity in materials can be attributed to an asymmetric center of the crystalline structure or molecular chain, which Piezoelectric actuators are unique driving force-generation devices, which can transfer input electric energy into force, displacement, or movement outputs efficiently and precisely via piezoelectric effect-based electromechanical coupling instead of electromagnetic induction. In comparison with traditional electromagnetic actuators, the most important features of the piezoelectric actuators are their compact size, flexible design, and ability to provide nanometer or sub-micrometer positioning. Here, recent progress in nonresonance piezoelectric actuators including multilayer ceramic actuators, step motors, inertial motors, and resonance ultrasonic motors, such as linear motors, rotary motors, multidegree of freedom motors, and microelectromechanical system actuators, is comprehensively presented. The working p...
